High speed battery charging system with high accuracy voltage sensing

Abstract

A battery charging system 100 is provided which comprises a charger 101 and a battery pack 102. The battery pack 102 comprises a battery cell or cells 150, memory means 140, temperature sensing means 147, and a high accuracy, high impedance voltage sensing means 112 that senses voltage directly at the battery cell terminals 151, 149. By sensing directly at the cell terminals 151, 149, charging error due to parasitic conductor impedances 132, 138 can be eliminated. The voltage sensing means 112 allows memory 140 and thermistor 147 data to be multiplexed, allowing the system to operate with four or fewer battery terminals.

What is claimed is: 
     
       1. A system for charging a battery comprising (a) A power supply for providing power output having a return line;   (b) A means for converting voltage and current levels;   (c) A means for controlling power conversion means having one or more terminals;   (d) A battery comprising Protection circuitry for opening a circuit under fault conditions;   Memory circuitry for storing identification and instruction data;   Temperature sensing means for sensing a temperature of one or more cells;   An energy storage cell with positive and negative terminals;   External terminals for power input and output and data;     (e) Interface circuitry for interpreting data from said memory means and said temperature sensing means;   (f) A means for accurately sensing voltage directly at the positive and negative terminals of said battery cell;   (g) A switch means comprising at least four switches, S1, S2, S3 and S4 wherein Opening all four switches activates said voltage sensing means and deactivates both said memory means and said temperature sensing means;   Closing S1 and S2 while opening S3 open activates said memory means and deactivates both said voltage sensing means and said temperature sensing means;   Closing S3 and opening S1 and S2 activates said temperature sensing means and deactivates both said voltage sensing means and said memory means;   S4 is connected as to be closed when both S1 and S2 are closed and otherwise be open.     
     
     
       2. A device as described in claim 1 wherein the external terminals for power input and output of data comprise a number selected from the group consisting of 1, 2, 3, or 4 terminals. 
     
     
       3. A device as described in claim 2 wherein a series resistor connected between the negative terminal of said energy storage cell and the inverting input of said high input impedance differential amplifier comprises a thermistor. 
     
     
       4. A device as described in claim 1 wherein the means for sensing voltage comprises a high input impedance differential amplifier with an output and inverting and non-inverting inputs with: The non-inverting input connected to the positive terminal of said energy storage cell through a series resistor;   The inverting input connected to the negative input of said energy storage cell through a series resistor;   The output connected to the power controlling means.   
     
     
       5. A device as described in claim 1 wherein the means for sensing voltage comprises A voltage reference source;   A comparator with an output and an inverting and non-inverting input, wherein the inverting input is connected to the positive terminal of said energy storage cell, and the voltage source is connected in series with the negative terminal of said energy storage cell and the non-inverting input.   
     
     
       6. A device as described in claim 1 wherein Said means for sensing voltage comprises an analog to digital converter with analog input connected to the positive terminal of said energy storage cell, and the return line connected to the negative terminal of said energy storage cell;   Said switch means comprises a 2-input, 1-output multiplexer with one input connected to the output of the analog to digital converter and the other input connected to said memory means.   
     
     
       7. A device as described in claim 1 wherein the means for sensing voltage comprises a microprocessor with on-board memory means and two or more on-board analog to digital converters wherein One analog to digital converter input is connected to the positive terminal of said energy storage cell;   One analog to digital converter input is connected to said thermal sensing means;   The return terminal of said microprocessor is connected to the negative input of said energy storage cell.